#2: You must be signed in when you transfer games (or the store has to be up) to confirm that you purchased said games and are not running a hack.
I don't use my Vita for music, so can't address #1 and #3, but I just wanted to second what Asphaltum said about #2. It makes complete sense for Sony to want to ensure you're the owner and aren't trying to game share, pirate, etc.
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